Not sure I am happy with first tow.

[westies]

Truck below has about 1000 Km on it when we left for Kelowna. Had some hard long hills to pull and then down the otherside. First hill is up about 23Km long and has some long 6 and 7 percent grades. Going down was about the same.

First in direct comparison with my 01 F**d PSD. The fuel milage was about the same at 11.66 mpg. The Duramx was definately quieter and much smoother ride. However, I know I pulled the same hills as fast or faster with the PSD. Coming down the other side I found the Duramax had a tendency to over rev if you were not watching it. I was in the tow/haul mode through this part of the trip. I should mayabe add that the Duramx is within 100 pounds lighter than the PSD. Coming back I decided to use tow/haul again and it works nice going up the hills. Coming down this time it hit 3500 rpm twice when gearing down. Enough, I took it out of tow/haul and just geared down. Probably a little harder on the brakes but never got close to over revs.

Now the question is..............did I drive this truck right and should I be concerned with the 3500 rpms? The fiver I was pulling probably comes in at 11500 lbs. I should add that on the flats and slight grades the PSD is no where close to the Duramax. Wife is so pleased with it she even let me get the Putco 4 inch tubes for it........Now thats a plus.

[ 04-21-2002: Message edited by: westies ]</p>

[bearman]

Hey westies
Ya, 3500 rpm in T/H is no big deal, my 2001 and 2002 does this on steep hills, it's the grade braking. You must rember the computer will not let the engine over rev. How many km you got on it now, I have found with both my dmax trucks as your milage increases, so does your power up to about 10000 km. My first pull with my 2002 was at 5500km, and I wasen't real impressed, now at 11000 km it pulls like a mule.
Cheers
Bear

On edit: I see you only have 1000km on it, wait for it, it will be great :D :D

[ 04-21-2002: Message edited by: bearman ]

[ 04-21-2002: Message edited by: bearman ]</p>

[Southard]

If you take a look at the tach you will notice that the hard redline actually starts at about 4700 rpm. The redline that starts at 3300 rpm is not the true redline. I have seen mine go a little above 3500 rpm while going down a mountain with a trailer that weighed 12,500 pounds. The first time it did this, I got real concerned really quick but then I looked closer at the tach and just started trusting the transmission.

I now have almost 34,000 miles on mine with no trouble out of the engine. Around 80% or more of my driving is while towing either a large 5th wheel that catches wind like a parachute, or while towing a backhoe and grossing out above 29,000 pounds. My only real complaint is the continual downshifting from 5th to 4th.

[NutNbutGMC]

^... Not dinging on anyone at all. One has to expect the downshift. That's what the lower gears are for, is to work. 5th is basically an overdrive gear ratio. I'd be happy that it IS using the gears for working properly. ;) ;) :cool:

[RealBigTruck]

Yep, same feeling here. I just towed a 24ft enclosed trailer weighing in at 7,000# a few hundred miles. Mileage was a little lower than I expected, right around 12. Going up a 6% grade I was down around 55mph. Of course, my truck only has about 800 miles on it, so I'm hoping to see better towing mileage and a little more power as the miles pile on.

Compared to my 94 Ford IDI Turbodiesel, the Dmax kicks butt. The same grade would have seen me at 35mph and about 7 mpg.

[madmax7]

IMO, the tow haul mode helps with grade braking, but is not the final word. Without a jake brake, grade and weight can push the truck faster in some cases than you want it to. Although braking is required, the grade brake function of the tow/haul mode is helpful and better than not having it.

As far as the ECM not allowing the engine to go over 3500 RPM, I am not sure what say it has when the torque is being forced through the tranny. I think you could over- rev. Maybe I am missing something here.

[Lone Eagle]

I just got back from my first pull from northern Utah to Twin Falls, Idaho with my 8K fifth wheel. I used tow/haul/race mode everywhere except in town. I put the cruise control on 70 and let the transmission shift up and down on it't own. There are a lot of 4 to 6 % hills on this route. It shifted down after loosing 4 mph in OD and pulled back up in fourth to 68 on the steepest grades without working up a sweat. It never gained more that a couple mph down hill in OD. This is the first truck my wife would drive while towing. It is better than I hoped for. Later! Lone Eagle :D :D :D

[Jackmchome]

I tow a 15000lb fifth wheel trailer. To get into, or out of, California you must go over a mountain somewhere. Quite often I will see my tach in the 4300 to 4500 range. I then brake down to about 3500 and let it work it's way up again. This is how the system is designed to work. As said by others, the allison will not let the engine be over reved. (about 4800) Use it, it works!

[ 04-23-2002: Message edited by: Jackmchome ]</p>

[RealBigTruck]

Hmmm...I think I might need to reconsider. Going up some decent grades in 6th (ZF-6) I'd start losing speed from 70mph downt to 60mph. I downshifted to 5th and stomped on it and it climbed all the way back to 70 at right around 3100rpm.

So it has the power to pull, I was just in the wrong gear! Without the auto tranny now I have to worry about the dummy behind the wheel.

Any issues with running the truck up at such a high RPM? If I shift back to 6th it just starts slowing again. Of course, I could always just take it easy and climb at 60 or 65mph. I was just seeing what it would do today.

I do have to say that it's way too easy to find myself towing 8,000 over 75mph on the flats. I keep surprising myself when I look down at the speedo. I'm going to have to start using cruise just to keep is safe.

Gary

[Kansas Kid]

RealBigTruck,

you really won't hurt anything by running the Dmax at 3100rpm other then your fuel economy. You can be sure that at those kind of rpm it is sucking the fuel down pretty good. If it was me, and the truck stabilized at around 60mph going up those grades, I would just leave it in 6th. Unless of course you are in a hurry, or are passing some Fords or Dodges, then I might see the need for running it in 5th gear. :D But if the truck continues to lose speed and goes under 60mph (about where peak torque is at in OD) it is much better to shift down then to lug the motor. Thats how I've down with every diesel pickup I pull with.

btw, I'm curious if the truck will stabilize at about 60mph and run there in OD. I'm not lucky enough to own a Dmax/ZF yet, and am kind of curious how it tows in OD

[02DMAX]

I had the high reving experience when coming down from Plymouth CA, 9,000# 5th wheel. Not overly concerned due to previous posts. My question is that once off the grade the truck took a number of minutes before the transmision would upshift. Any trick to make it upshift ?

2002HD D/A EC LB 2WD

[westies]

OK............second trip out and things have changed considerably. Fuel consumption up 1.5 mpg, and more power than I really need. Let the tranny do its own thing and it ran flawlessly.
When I arrived at Spokane I was in camp ground with 8 other fivers and all being pulled with a PSD. I would think at least 6 of the owners were over Saturday morning wanting a good look at mine. Three of them knew I have been heavy PSD and of course that was a surprise when they had seen I switched. After the all the talk, I would bet at least two of them will be driving a Duramax within the next 6 months. The other four maybe the next six months after. Of course my wife had to tell the other wives how comfortable and quiet ours is, so there is a good chance the above changes may happen sooner. :D :D :D

[Calgary]

Westies - pleased to hear that the 3500 is meeting your expectations and that you're now happy with the shifting.

Just got all of the equipment installed on mine last week and broke 1,000 kms. today. Very quiet and a very smooth shifting tranny.

Hope to get over to Oliver, BC within the next ten days to pick up my fiver - still waiting on some back-ordered furnishings.

Happy truckin'.

[DmaxMaverick]

Great post, westies. I've heard several others with similar experiences, and I have a few of my own.

And to think GM dealers have the nerve to attempt to charge US for "advertising fee" on new trucks! It should be the other way around.